Facebook was pretty quick to respond and revert the changes. I think if they had waited for a few weeks most users would have forgotten about it. I doubt any significant percentage of users changed their facebook usage habits because of this issue.
Facebook can lose the grace of the masses in a matter of months.
Or even in weeks. That's the crucial issue. It's easy to bail out of websites and go elsewhere. The user experience has to be friendly, or a competitor has an easy grab on market share.
Now whether Facebook or anyone else can really monetize a social networking site is another question. "The market can remain irrational longer than you can remain solvent," so maybe Facebook will go broke before its customers bail out. But in any case, the customers can bail out if they don't like the overall experience.
